ARINC 424 - Nav Databases
 

Hi all,

Have pilots of FMS equipped aircraft using a Nav Database for RNP approaches (Jepp Nav DB for example), or other ‘overlay’ approaches such as VOR/NDB approaches, recently found approaches in the database disappearing unexpectedly? EGBJ NDB approaches have disappeared from our nav database but used to be available, also Lydd’s RNP approach has been removed. I am using a Leonardo type with a Jepp database, but keen to know if the same approaches have been removed from other types’ databases.

It appears rules in ARINC 424 coding do not allow the use of biased DME as a recommended navaid when programming an overlay approach, this is the reason NDB approaches for NQY 12/30 or GLO 09/27 are not available in the FMS, and that the use of biased DMEs are quite common in the UK. Lydd’s RNP approach has apparently been removed because the LNAV element of the missed approach was ‘unsafe’ - anyone happen to know more about this?

The concerning thing is that without trying to load these approaches you would be none the wiser until you came to need them, perhaps as an alternate. Not the end of the world to fly an NDB approach on the needles, but not ideal if the RNP approach was your alternate and it’s not there….

I can't vouch for all Leonardo types, but the reaon that some of the RNP approaches have disapperared is there is a problem with the software flying the approach (I believe it is some of the turns in, for instance, the GA). Apparently this will be corrected in a subsequent software phase, although this presupposes that you are getting the updated software in the future...